1. Field of the Invention
This invention relates to a stent crimping device and method of use of the type that will enable an end user to firmly crimp a stent onto the distal end of a catheter assembly.
2. Description of the Related Art
In a typical percutaneous transluminal coronary angioplasty (PTCA) procedure, for compressing lesion plaque against the artery wall to dilate the arterial lumen, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and advanced through the vasculature until the distal end is in the ostium. A guidewire and a dilatation catheter having a balloon on the distal end are introduced through the guiding catheter with the guidewire sliding within the dilatation catheter. The guidewire is first advanced out of the guiding catheter into the patient's coronary vasculature, and the dilatation catheter is advanced over the previously advanced guidewire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, a flexible, expandable, preformed balloon is inflated to a predetermined size at relatively high pressures to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile, so that the dilatation catheter can be withdrawn from the patient's vasculature and blood flow resumed through the dilated artery. While this procedure is typical, it is not the only method used in angioplasty. Further, other methods are well known in opening a stenosed artery such as atherectomy devices, plaque dissolving drugs, and the like.
In angioplasty procedures of the kind referenced above, there may be restenosis of the artery, which may require another angioplasty procedure, a surgical bypass operation, or some method of repairing or strengthening the area. To reduce the chance of restenosis and strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, typically called a stent. A stent is a device used to hold tissue in place or to provide a support for a graft or tissue joined together while healing is taking place. A variety of devices are known in the art for use as stents, including coiled wires and wire mesh sleeves, in a variety of patterns, that are able to be crimped onto a balloon catheter, and expanded after being positioned intraluminally on the balloon catheter, and that retain their expanded form. Typically the stent is mounted and crimped onto the balloon portion of the catheter, and advanced to a location inside the artery at the lesion. The stent is then expanded to a larger diameter, by the balloon portion of the catheter, to implant the stent in the artery at the lesion. Examples of stents and delivery catheters of the type described herein are disclosed in more detail in U.S. Pat. No. 5,102,417 (Palmaz); U.S. Pat. No. 5,514,154 (Lau et al.); and U.S. Pat. No. 5,569,295 (Lam), incorporated herein by reference.
However, if the stent is not tightly crimped onto the catheter balloon portion, when the catheter is advanced in the patient's vasculature the stent may slide off the catheter balloon portion in the coronary artery prior to expansion, and may block the flow of blood, requiring procedures to remove the stent.
In procedures where the stent is placed over the balloon portion of the catheter, the stent must be crimped onto the balloon portion to prevent the stent from sliding off the catheter when the catheter is advanced in the patient's vasculature. In the past, the crimping procedure was often done by hand, which may result in uneven force being applied, resulting in non-uniform crimps. In addition, it was difficult to judge when a uniform and reliable crimp had been applied or if the stent had damaged the balloon. Though some tools, such as ordinary pliers, have been used to crimp the stent, these tools have not been entirely adequate in achieving a uniform crimp.
There accordingly remains a need for improved tools and methods to secure stents on the balloon portions of catheters.